A variety of winglet designs are known. Many winglets are of a type that comprise an upwardly orientated planar winglet blade, attached to the end of the aircraft wing via a short, curved, transition zone. Examples of winglets of this type are shown, for example in U.S. Pat. Nos. 5,275,358 and 5,348,253.
Some alternative types of winglet design have also been proposed. For example, EP 1349778 discloses a winglet having an increasing radius of curvature as it extends from its inner end to its outer end. EP 1349778 discloses the possibility of the winglet following a generally elliptical curve.
The design of winglets to date has been primarily dictated by aerodynamic considerations, such as their impact on total drag (typically generating a reduction in induced drag and a (smaller) increase in profile/viscous drag). Structural considerations have tended to be a secondary focus in the design process.